Solidification/stabilisation behaviours of Zn²⁺ in magnesium potassium phosphate cement: Experiments and density functional theory study

The solidification/stabilisation behaviours of Zn²⁺ in magnesium potassium phosphate cement (MKPC) have not been thoroughly investigated. Herein, a series of experiments and a detailed density functional theory (DFT) study were conducted to investigate the solidification/stabilisation behaviours of Zn²⁺ in MKPC. The results showed that the compressive strength of MKPC reduced with the addition of Zn²⁺ because the formation of MgKPO₄·6H₂O (the main hydration product in MKPC) was delayed with the addition of Zn²⁺, as discovered by the crystal characteristics, and because Zn²⁺ exhibited a lower binding energy in MgKPO₄·6H₂O compared to Mg²⁺, as revealed by DFT results. Additonally, Zn²⁺ had little influence on the structure of MgKPO₄·6H₂O, and Zn²⁺ existed in MKPC as the formation of Zn₂(OH)PO₄, which was decomposed in the range of around 190–350 °C. Moreover, there were a lot of well-crystallised tabular hydration products before the addition of Zn²⁺, but the matrix was comprised of irregular prism crystals after adding Zn²⁺. Furthermore, the leaching toxicity of Zn²⁺ of MKPC was much smaller than the requirements of Chinese and European standards.